Any sources for this proposal? As far as I know, "tipping down" wouldn't be used this way in AE.

Ich kenne

It's tipping it down., allerdings scheinen hier beide Versionen möglich:

be tipping (it) down UK informal › When it is tipping it down, a lot of rain is falling: We won't be able to go to the beach today - it's tipping it down.
http://dictionary.cambridge.org/dictionary/br...

marcleipzig, ein Neuvorschlag für das Wörterbuch ist löblich, aber bitte bring auch ein paar Belege dafür. Siehe auch die 'Hinweise', die automatisch erscheinen, wenn du hier einen Beitrag postest.

My understanding, regarding AE, is the same as hbberlin's.

tipping down - schütten, gießen

IF this does ever evolve into an entry that's has enough backing to be included in Leo, it definitely needs to be marked "BE."

http://dictionary.cambridge.org/dictionary/br...
be tipping (it) down UK informal
› When it is tipping it down, a lot of rain is falling: We won't be able to go to the beach today - it's tipping it down.

http://www.macmillandictionary.com/dictionary...
it is tipping (it) down
British informal
it is raining a lot

http://www.theguardian.com/stage/2004/aug/11/...
It's tipping it down at the Edinburgh festival. Two days, solid.

http://www.theguardian.com/music/2014/jun/27/...
If it's muddy and tipping it down, Glastonbury audiences seem to vastly prefer a kind of musical comfort blanket: they're after stuff they know rather than intrepidly exploring the unknown.

I prefer it's tipping it down, like Gibson.

I leave the German side to the native speakers.

it is/was 'tipping (it) down
(British English, informal) it is/was raining heavily
http://www.oxfordlearnersdictionaries.com/def...

It's tipping it down
We use this expression humorously to describe a rainy day.
spoken, informal
Example 1
What a terrible day! There's no way we can play football outside.
Yes, it's really tipping it down.
Example 2
How was the barbecue on Friday?
Not great. It tipped it down all evening.
http://www.ihbristol.com/english-phrases/exam...

Silverstone is blanketed in low, grey clouds, and it's raining - at first not that hard, but now it's tipping it down.
http://news.bbc.co.uk/sport2/hi/motorsport/fo...

Water, water everywhere
It's tipping it down at the Edinburgh festival. Two days, solid. They're huddled under the Pleasance Courtyard, and handing out brollies to the queue at the Stand Comedy Club. The forecourt of the Underbelly looks like an epic site-specific production of The Tempest. How to explain the extraordinary fact that it's raining in Scotland?
http://www.theguardian.com/stage/2004/aug/11/...

Noch ein paar BE-Belege für it is/it's/it was tipping it down.

für mich ist das immer noch: es schüttet - someone up there is tipping a bucket over and it's bucketing down...

As noli points out, "it's bucketing down" is already in the dictionary, so here's an entry based on the existing entry.

(Although it occurs to me that I'd say "bucketing it down", too.)

Das KANN nur BE sein. Nie gehört...

@ papousek: not to mention "throwing it down", "chucking it down" or even "pissing it down"

Es regnet - nein, es schüttet, es pladdert, es kübelt, es gießt.
http://www.faz.net/aktuell/reise/fern/austral...

Für Regen fallen mir mehrere Beschreibungen ein:
- es schüttet (wie aus Kübeln /Eimern)
- es pladdert
- es regnet Bindfäden /Schusterjungs bzw. -buben /Katzenköppe
- es gießt
http://de.etc.sprache.deutsch.narkive.com/8z9...

Wann immer wir den Fernseher einschalten zur Fußball-Übertragung, sehen wir: es regnet. Nun ja, manchmal gießt es auch oder schüttet, plästert, pladdert oder schifft, mal in Strömen, mal wie aus Kübeln oder auch wie aus Eimern.
http://jungle-world.com/jungleblog/265/

Weitere dt. Möglichkeiten:
Es kübelt wie blöd.
Es kübelt wie aus Eimern.
Es kübelt nur so runter.

Es pladdert. [Norddt.]

Es regnet Bindfäden/Schusterbuben (etc.). [Norddt.]?

Es schifft.

"It's bucketing down" and "bucketing it down" are also clear candidates for BE, although AE would say "it's raining buckets."

@ hbberlin -- both the BE variants (bucketing it down) and AE (raining buckets) are already in the dictionary, and marked as such.

LEO:
to rain hard - stark regnen
to be pouring with rain - in Strömen gießen
It's pouring with rain. - Es gießt in Strömen.
It's raining hard. - Es regnet stark.
The rain came down in sheets. - Es goss in Strömen.
The rain fell in sheets. - Es goss in Strömen.
to rain cats and dogs [coll.] - Bindfäden regnen
to rain cats and dogs [coll.] - in Strömen regnen
It's pouring. - Es regnet in Strömen.
It's tipping down. [coll.](Brit.) - Es regnet in Strömen
It's tipping it down. [coll.](Brit.) - Es regnet in Strömen
It's bucketing down. [coll.](Brit.) - Es gießt wie aus Eimern.
It's bucketing down. [coll.](Brit.) - Es schüttet wie aus Kübeln.
It's raining buckets. (Amer.) - Es gießt wie aus Eimern.
It's raining buckets. (Amer.) - Es schüttet wie aus Kübeln.

related discussion: chucking it down - #5
(and the rest of that thread, and the threads linked in #5)

*edit*

That was strange; LEO only posted part of what I had pasted. Trying once more ...

It also didn't post my comment (even though that's supposedly a required field), which was (WTTE):

This is just an additional suggestion that has evidently been made a time or two in passing but may have been overlooked.

I have no opinion about which of the many options to put for the German side.

are the "sheet" entries AE?

When the poet John Keats moved to Teignmouth, the rain fell in sheets and heavy mists rolled in from the sea.
http://www.exeter.ac.uk/news/events/details/i...

The rain was just coming down in sheets so's the water was dripping over my ears and you couldnt use the Walkman.
http://www.dsl.ac.uk/entry/snd/sndns3848

For some time it rained in sheets driven violently by the gale, and I got what little shelter I could as I walked from the high hedges.
http://www.homepages.ucl.ac.uk/~ucjtjur/1920s...

Surely that's for BE speakers to answer, but I wouldn't have thought so. There seem to be BE hits for it.

thanks for the info. Ah well, better start expanding my vocabulary to include dated and Scots ;-)